First: I'm going to have to dig around to refresh my memory on the ideal end gap, but I'm thinking 0.003" - 0.004"/bore inch should be spec for these rings.

Which tells me these are severely worn showing 0.027" at the major thrust point of the bore. Orta be closer to 0.012" - 0.016", *I think*. (famous last words).

Secondly: Measureing the ring end gap at the unworn portion at the bottom of the bore and then again at the major thrust point about an inch below the top of the bore reveals a ring end gap difference from 0.0235" to 0.027", or 0.0035".

If we devide 0.0035" by pi we learn the bores have a tiny bit more than 0.001" of taper.

Translation: Who cares? That's not enough to worry about. Though I do have a fresh set of barrels that were cut for these 1050 pistons at the same time as the set that's in use.

Why? Because pistons don't usually wear very much. It's the rings and iron bores that do most of the wearing.

ie: New rings and the the fresh cyls and these pistons could go back to work at practically new spec. But for 0.0011" taper, I'm not done with the old ones yet.

Those are my favourite feeler guages. Can't find them like that anymore. Lost the 0.0015" a few years ago when I loaned them to a workmate.

Here's a good shot of the relief or "counter bore" in the case that Anton was talking about in Notrex's thread. If you can imagine the corresponding shape on the base of the cylinder spigot, you'll understand what he needs to turn down before he can fit the nikasil cylinder to the earlier case which has no relief or "counter bore" segment.

Not sure about this, guy I bought it from used the word Rennsport. That said I did check the number but I don't recall, but I think it was a 336 stamped on the end.
Snowbum briefly talks about it hear: Mods.

At any rate, my bike kicks in at about 4Krpm like no other airhead I ever rode. It's a real blast to ride.